[PATCH 13/24] sched: Update rq clock on nohz CPU before setting fair group shares

From: Frederic Weisbecker
Date: Thu Dec 20 2012 - 13:34:09 EST

Because we may update the execution time (sched_group_set_shares()->
update_cfs_shares()->reweight_entity()->update_curr()) before
reweighting the entity after updating the group shares and this requires
an uptodate version of the runqueue clock. Let's update it on the target
CPU if it runs tickless because scheduler_tick() is not there to maintain

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Alessio Igor Bogani <abogani@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Geoff Levand <geoff@xxxxxxxxxxxxx>
Cc: Gilad Ben Yossef <gilad@xxxxxxxxxxxxx>
Cc: Hakan Akkan <hakanakkan@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
kernel/sched/fair.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 59e072b..a6ddc1e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5837,6 +5837,12 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
se = tg->se[i];
/* Propagate contribution to hierarchy */
raw_spin_lock_irqsave(&rq->lock, flags);
+ /*
+ * We may call update_curr() which needs an up-to-date
+ * version of rq clock if the CPU runs tickless.
+ */
+ update_nohz_rq_clock(rq);
for_each_sched_entity(se) {
/* update contribution to parent */

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